In order to prevent possible engine damage, it is desirable to preclean the combustion air on an internal combustion engine. Customarily, the engine intake air passes through a filter apparatus to remove entrained particulate matter from the intake air stream prior to entering the combustion chamber of the engine. Such filter apparatus, frequently referred to as air precleaners, are used not only on combustion engines for powering vehicles, but are also commonly used on diesel engines in general, including for example the diesel engines which power the compressors and fans on transport refrigeration units.
One type of filter apparatus commonly used in connection with such combustion engines comprises an essentially cylindrical, pot-like housing defining a filter chamber that houses an annular cartridge-like filter element. An end cover, mounted to the open end of the filter housing, retains the filter element within the housing. The filter element has an axially extending, central bore, that defines an outlet chamber for filtered, that is clean, air. Being axially centered within the housing, the filter element, in conjunction with the surrounding wall of the housing, defines an axially elongated, annular unfiltered air inlet chamber positioned radially outwardly of and circumscribing the filter element.
In operation, incoming unfiltered engine intake air passes into the annular inlet chamber, typically, either tangentially through one or more openings in the wall of the housing or axially through a plurality of openings formed along a radially outer circumferential path in the end cover. From the inlet chamber, the unfiltered engine intake air passes generally radially through the filter element into the clean air outlet chamber defined by the central bore. As the intake air passes through the filter element, typically drawn by suction from the engine, entrained particulate contaminant matter is removed. The filtered engine intake air passes from the central outlet chamber through a central opening in the end cover and thence to the combustion air manifold for supply to the combustion chamber of the engine.
As the incoming engine intake air is drawn by suction from the engine through the filter element, the pressure of the air drops. As a result, a pressure differential exists between the inlet air chamber and the outlet air chamber. Consequently, the incoming unfiltered air has a natural tendency to seek a path of least resistance around the ends of the filter element and into the clean air outlet chamber. As such bypass leakage results in unfiltered, contaminated air passing directly into the clean air outlet chamber, and thereafter into the combustion chamber of the engine, it is desirable to provide a seal at each end of the filter element to preclude unfiltered, contaminated air from bypassing the filter element.
For example, it is common in the art to provide a gasket seal at the interfaces of the respective axial ends of the filter element and housing and the end cover, respectively. However, due to improper positioning, vibration during operation, slack tolerances and other reasons, the seal between the gasket face and the end of the element or the housing or the end cover, as the case may be, may not remain air tight and leakage across the seal may result. Gasket seals may also leak in operation due to vibration, improper positioning of the filter element or other factors.